Printed circuit cards, for example, are commonly tested for defects before they are used. These defects can arise from screening or solder joint problems. Defects are tested for by simulating the environment in which the circuit card will be used. For instance, in aerospace applications, such as for the Space Shuttle, circuit cards are tested under conditions simulating actual environmental conditions of high pressure, temperature, moisture, high vibration and shock.
In the past, high vibration and shock have been tested by placing the circuit cards, or other components in various types of test fixtures which are then attached to a shaker. The fixture can be arranged for testing six-axis shock and three-axis vibration in a typical test for screening or solder joint problems in the circuit boards under test.
One prior art test fixture comprises a box with a door which opens into a hollow interior region for mounting the circuit cards. The circuit cards under test slide into fixed slots on opposite sides of the test fixture interior. The door of the fixture is then closed, and the fixture is subjected to shock and vibration testing. This fixture has several disadvantages. For instance, the fixed slots within the fixture are useful in only mounting individual cards of the same size. If a board failure develops, the circuit card can slide out and be replaced; but the fixture uses hydraulics for locking the door and clamping onto the boards, and hydraulics can be a source of contamination. The fixture is generally hollow with no internal support for the cards which are subject to undesired bending loads during vibration testing.
The present invention provides a test fixture which overcomes these problems and also provides additional improvements described below.